linux-kernel - Re: [PATCH iwl-next 9/9] igc: Add support to get frame preemption statistics via ethtool

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Message-ID: <57139951-daf7-42c3-b7a6-e4870a3f71fa@linux.intel.com>
Date: Mon, 23 Dec 2024 17:52:37 +0800
From: "Abdul Rahim, Faizal" <faizal.abdul.rahim@...ux.intel.com>
To: Vladimir Oltean <olteanv@...il.com>
Cc: Tony Nguyen <anthony.l.nguyen@...el.com>,
 Przemek Kitszel <przemyslaw.kitszel@...el.com>,
 Andrew Lunn <andrew+netdev@...n.ch>, "David S . Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
 Jesper Dangaard Brouer <hawk@...nel.org>,
 John Fastabend <john.fastabend@...il.com>,
 Vinicius Costa Gomes <vinicius.gomes@...el.com>,
 intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH iwl-next 9/9] igc: Add support to get frame preemption
 statistics via ethtool



On 17/12/2024 12:05 am, Vladimir Oltean wrote:
> On Mon, Dec 16, 2024 at 01:47:20AM -0500, Faizal Rahim wrote:
>> Implemented "ethtool --include-statistics --show-mm" callback for IGC.
>>
>> Tested preemption scenario to check preemption statistics:
>> 1) Trigger verification handshake on both boards:
>>      $ sudo ethtool --set-mm enp1s0 pmac-enabled on
>>      $ sudo ethtool --set-mm enp1s0 tx-enabled on
>>      $ sudo ethtool --set-mm enp1s0 verify-enabled on
>> 2) Set preemptible or express queue in taprio for tx board:
>>      $ sudo tc qdisc replace dev enp1s0 parent root handle 100 taprio \
>>        num_tc 4 map 0 1 2 3 0 0 0 0 0 0 0 0 0 0 0 0 \
>>        queues 1@0 1@1 1@2 1@3 base-time 0 sched-entry S F 100000 \
>>        fp E E P P
> 
> Hmm, the prio_tc_map pattern changed since the last time I looked at igc
> examples? It was in decreasing order before? How do you handle backwards
> compatibility with the Tx ring strict priority default configuration?
> I haven't downloaded the entire set locally, will do so later.
> 

I tested like this for i226:
     CMD=(
         "tc qdisc replace dev $IFACE parent root handle 100 taprio "
         "num_tc 4 "
         "map 3 2 1 0 3 3 3 3 3 3 3 3 3 3 3 3 "
         "queues 1@0 1@1 1@2 1@3 "
         "base-time $BASE "
         "${SCHED_ENTRY[*]} "
         "flags 0x1 "
         "txtime-delay $TXTIME_DELAY "
         "clockid CLOCK_TAI "

But I mistakenly copied the mapping from a different scenario where socket 
priority -> tc -> hw_queue mapping is not important to my test objective in 
that scenario.

I'll update the description to use decreasing order then.

>> +
>> +	return ooo_smdc + ooo_frame_cnt + ooo_frag_cnt + miss_frame_frag_cnt;
>> +}
>> +
>> +static void igc_ethtool_get_mm_stats(struct net_device *dev,
>> +				     struct ethtool_mm_stats *stats)
>> +{
>> +	struct igc_adapter *adapter = netdev_priv(dev);
>> +	struct igc_hw *hw = &adapter->hw;
>> +
>> +	stats->MACMergeFrameAssErrorCount = igc_ethtool_get_frame_ass_error(dev);
>> +	stats->MACMergeFrameSmdErrorCount = 0; /* Not available in IGC */
>> +	stats->MACMergeFrameAssOkCount = rd32(IGC_PRMPTDRCNT);
>> +	stats->MACMergeFragCountRx =  rd32(IGC_PRMEVNTRCNT);
>> +	stats->MACMergeFragCountTx = rd32(IGC_PRMEVNTTCNT);
>> +	stats->MACMergeHoldCount = 0; /* Not available in IGC */
> 
> Don't report counters as zero when in reality you don't know.
> 
> Just don't assign values to these. mm_prepare_data() -> ethtool_stats_init()
> presets them to 0xffffffffffffffff (ETHTOOL_STAT_NOT_SET), and
> mm_put_stats() -> mm_put_stat() detects whether they are still equal to
> this value, and if they are, does not report netlink attributes for them.
> 

Got it.


>> diff --git a/drivers/net/ethernet/intel/igc/igc_regs.h b/drivers/net/ethernet/intel/igc/igc_regs.h
>> index 12ddc5793651..f40946cce35a 100644
>> --- a/drivers/net/ethernet/intel/igc/igc_regs.h
>> +++ b/drivers/net/ethernet/intel/igc/igc_regs.h
>> @@ -222,6 +222,25 @@
>>   
>>   #define IGC_FTQF(_n)	(0x059E0 + (4 * (_n)))  /* 5-tuple Queue Fltr */
>>   
>> +/* Time sync registers - preemption statistics */
>> +#define IGC_PRMEVNTTCNT		0x04298	/* TX Preemption event counter */
>> +#define IGC_PRMEVNTRCNT		0x0429C	/* RX Preemption event counter */
>> +#define IGC_PRMPTDRCNT		0x04284	/* Good RX Preempted Packets */
>> +
>> + /* Preemption Exception Counter */
>> +#define IGC_PRMEXPRCNT					0x042A0
>> +/* Received out of order packets with SMD-C and NOT ReumeRx */
>> +#define IGC_PRMEXPRCNT_OOO_SMDC 0x000000FF
>> +/* Received out of order packets with SMD-C and wrong Frame CNT */
>> +#define IGC_PRMEXPRCNT_OOO_FRAME_CNT			0x0000FF00
>> +#define IGC_PRMEXPRCNT_OOO_FRAME_CNT_SHIFT		8
>> +/* Received out of order packets with SMD-C and wrong Frag CNT */
>> +#define IGC_PRMEXPRCNT_OOO_FRAG_CNT			0x00FF0000
>> +#define IGC_PRMEXPRCNT_OOO_FRAG_CNT_SHIFT		16
>> +/* Received packets with SMD-S and ReumeRx */
> 
> What is ReumeRx?

Resume receive. It’s a typo in the i226 documentation that I (shamelessly) 
copied into the code without checking properly. It's meant to indicate that 
an RX flag in the i226 firmware is set. I’ll remove the 'ResumeRX' part 
since it adds confusion.